Import spritesheet into Tiled. Create your map (separate into layers and create colliders as needed). In Tiled2Unity, Help, Import Tiled2Unity into a Unity project. In Tiled2Unity, File, Open a file, then press the big ass export button. Go to Assets, Tiled2Unity, Prefabs in your Unity project, and drag your map onto the scene editor. Add a player and scripts to interact with the map layers, and you have a level.